Effect Of Long-Term Fertilization On Phosphorus Behavior In Purple Soil

As the macronutrient for plants, phosphorus (P) is the main yield limiting factors in agriculture. Recent years, more and more P fertilizer were applied in agriculture soil, so agriculture soil accumulated a large of P, and the function of P fertilizer reduced. Scientists have gone deep into the forms of P, the dynamic change of P, and the P availability, but it were studied very few on P accumulation, the change of P forms, and the availability under long-term different fertilization conditions. Also, there was not have systematically study on Charicteristics and availability of inorganic P, organic P under long-term different fertilization conditions. In this research, the experiment was carried out to study the effect on P accumulation, the forms and availability of soil P of long-term different fertilization treatments, and to study on P fertilizer utilization efficiency and yield effection by using long-term fertilization experiment and laboratory analysis method, which is one typical soil of the National Monitoring Base of Soil Fertility and Fertilizer Efficiency.The aim was to provide a scientific theory of P fertilizer application and management for rice-wheat rotation system in purple soil. The main results were as follows:The results of 15 years located fertilization showed that the content of TP and Olsen-P decreased in purple soil (10-20cm, 20-40cm) whith non P fertilization treatments. TP decreased 22.8% in the two soil profiles, the average decrease content of soil TP was 9.9 mg·kg^-1. Olsen-P decreased 76.6% in the two soil profiles, the average decrease content of soil Olsen-P was 0.2mg·kg^-1. The content of TP and Olsen-P increased in different P fertilization treatments of purple soil. TP increased 0.2 times in the two soil profiles, the average increase content of soil TP was 6.4 mg·kg^-1. Olsen-P increased 3.1 times in the two soil profiles, the average increase content of soil Olsen-P was 0.9mg·kg^-1. The average increase content of soil Olsen-P were 1.7mg·kg^-1 in P fertilizer+manure treatments, 1.5mg·kg^-1 in P fertilizer treatments, so P fertilizer+manure treatments could improve the rate of P accumulation.The effect on TP content and Olsen-P content decreased with the increase of the depth of the soil profiles in every treatment. In P fertilization treatments, the rate of Olsen-P accumulation and the content of Olsen-P accumulation lower in 20-40cm soil profile than in 0-20cm soil profile. Compare with 20-40cm profile, more 101.4mg·kg^-1 TP and 17.5 mg·kg^-1 Olsen-P increased in 0-20cm profile of P fertilization treatments; more 164.6mg·kg^-1 TP decreased in 0-20cm profile of non P fertilization treatments.In Purple soil, about 70% of the soil TP was inorganic P. The average content of inorganic P in the two soil profiles was 443.6mg·kg^-1. The content sequence of forms of inorganic P was Ca₁₀-P> O-P>Fe-P>Al-P>Ca₈-P>Ca₂-P; About 30% of the soil TP was organic P. The average content of organic P in the two soil profiles was 196.3mg·kg^-1. The content sequence of forms of organic P was Moderately labile organic P (MLOP)>Moderately resistant organic P (MROP)>Highly resistant organic P (HROP)>Labile organic P (LOP). The content of organic P and inorganic P decreased with the increase of the depth of the soil profiles.In different P fertilization treatments, Total organic P, every form of organic P, Total inorganic P and every form of inorganic P had more content than different non P fertilization treatments.The correlativity sequence of every organic P form with Olsen-P was LOP>MLOP>MROP> HROP. The correlativity sequence of every inorganic P form with Olsen-P was Ca₂-P>O-P>Fe-P > Ca₈-P > Al-P > Ca₁₀-P. The correlativity of every inorganic P form with Olsen-P, and the correlativity among every inorganic P form were better than every organic P form'. The correlativity in 0-20cm soil profile was better than in 20-40cm soil profile.In wheat-rice rotation, P fertilizer utilization efficiency increased during the past 15 years. P fertilizer utilization efficiency of wheat and rice were 20% and 13.8% in the first 5 years, 33.8% and 25.6% in the second 5 years, 49% and 25.2% in the last 5 years respectively. P fertilizer utilization efficiency were very low, so there were a large of P accumulation in Purple soil.The research on P balance showed that P had deficit 273.8kg·hm^-2 in different non P fertilization treatments of purple soil, P had surplus 475.1kg·hm^-2 in different P fertilization treatments of purple soil. The increasing of soil Olsen-P caused by each 100 kg·hm^-2 P accumulation was 3.27mg·kg^-1 in Purple soil. The result could be used to predict the long-term change of soil available P by annual P budget, and would provide useful information to properly manage P fertilization. If the soil available P would be increase to 60mg·kg^-1 in the future, the demand of P fertilizer should be 6000-10000kg·hm^-2 in different P fertilization treatments.